Gun for atomization and electrostatic spraying of materials



Jan. 29, 1963 M. A. R. POINT 3,075,706

GUN FOR ATOMIZATION AND ELECTROSTATIC SPRAYING OF MATERIALS Filed May 9, 1960 Inventor niteri tats te The present invention relates to guns, particularly for hand use, for the atomization and electrostatic spraying of liquids, especially for spraying of materials which are electrically conductive, such as metallised paints or water paints. The invention has for its object to provide an improved gun having a head by means of which the paint is submitted to a double atomization due to two cooperating members.

In order that the invention may be more clearly understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawing which shows an axial longitudinal section of a gun according to the invention.

Referring to the drawing, the gun comprises a handle 1 to which is fixed in any appropriate manner an elongated body 2 of insulating material. Into the handle extend (a) a pipe 3 for the supply of paint under a pressure which has its outlet in a central rotating head member 4 of any convenient type having an atomization edge 4a, which head member can be of conducting, high resistivity or insulating material; (b) a high tension cable 5 connected, preferably through an electric protective resistance 6, to an electrode 7 which is fixed at the end of an extension Zn on the body 2; (c) a low tension cable 8 for supplying current to an electric motor 9 which is fixed to the gun.

The handle also comprises a trigger it operable by the user, which is associated with a rod 11 by means of which it can control a valve 12 connected in the paint supply pipe 3 and a switch 13 connected in the cable 8 in the circuit of the motor 9*.

The motor 9 drives the central head member 4 by means of an insulating shaft 14 having an extension rod 14a which passes through the end wall of the body 2 and is fixed to the hub portion 41) of the central head member 4. An insulating support 15 is fixed to the outer surface of the head member 4 in a manner such that it does not cover the tapering atomizing edge 4a of the head member. To the outer surface of the support 15 is fixed the internal surface of an outer electrostatic head member 16, care again being taken that the tapering atomizing edge 16a of the head member remains free. The head member 16 is made of metal or semi-conducting high resistivity material.

The radial dimensions of the support 15 and of the outer head member 16 are such that the rear edge of the head member 16 faces and is spaced a very short distance away from the electrode 7. If desired, in a modification, the electrode 7 can be constituted as a spring-pressed contact adapted to engage the head 16.

The motor 9 rotates the two head members 4 and 16 simultaneously, the paint being delivered to the central head member 4 and the high tension being applied to the outer head member 16. The paint may be delivered into an annular groove at the rear of the head member 4 and pass to the front part of this head member through apertures do in the hub 4b of the head member 4.

The operation of the device is as follows:

Paint supplied to the central head member 4 is submit- .ted to a first atomization (or distribution) due to the centrifugal force and the electric field existing between the two head members. Attracted by the outer head hfilhflhh Patented Jan. 29, 1%53 member 16, the paint becomes deposited thereon. The head member 16, connected to the source of high tension G, by the cable 5, produces a second atomization of the paint which is then directed towards the object 17 to be covered.

It will be seen that the potential of the central head member 4 is determined by the resistance of the column of paint. Thus with an electrically conducting paint this potential can be approximately earth potential. It is pointed out that this potential only exists during operation of the gun, that is when the head member 4 is electrically connected to the column of paint being supplied to it, and that this head member is electrically connected to the outer head member 16 by the atomized particles of material which are projected by the head member 4 on to the head member 16.

While a particular embodiment has been described it will be understood that various modifications may be made without departing from the scope of the invention as defined by the appended claims.

Thus, although in the embodiment shown in the drawing the two head members 4- and 16 rotate simultaneously in the same direction and at the same speed, in a modification the two head members can rotate in opposite directions and, if desired, at diflferent speeds. It sufiices mechanically to connect the two head members by means of pinions and appropriate gear wheels, subject to the condition that these gears maintain the electric insulation of the two head members in the same manner as the part 15. Each head member can alternatively be driven by a separate motor if this is advantageous in any particular application.

Further, instead of being constructed for hand use, the gun according to this invention may be constructed for fixing in position in a paint spraying machine.

I claim:

1. A spray gun for centrifugally and electrostatically atomizing and spraying a liquid coating material on to an object to be coated, said gun comprising a head having an inner rotatable electrically conducting member for effecting an initial atomization of the coating material by means of centrifugal force and including an edge by means of which the initially atomized coating material leaves said inner member, an outer electrostatic atomizing and spraying member to which the coating material leaving the edge of the inner member is attracted and including an edge which is radially spaced from the edge of the inner rotatable member and from which the eleotrostatically atomized particles of coating material are directed on to the object to be spray-coated, an insulating member for coaxially and mechanically interconnecting said inner and said outer members, means for applying a direct high potential to said outer electrostatic member, means for feeding liquid covering material to said inner member, and an electric motor fixed to said gun for rotating at least the inner member of said head.

2. A gun according to claim 1, wherein the outer electrostatic member comprises an active atomizing and spraying edge situated in front of the plane of the edge of the inner rotating member and also in front of the plane containing said insulating member.

3. A spray gun for centrifugally and electrostatically atomizing and spraying a liquid coating material on to an object to be coated, said gun comprising a head having an inner rotatable electrically conducting member of generally cylindrical shape for effecting an initial atomization of the coating material by means of centrifugal force and including an edge by means of which the initially atomized coating material leaves said inner member, an outer generally cylindrically electrostatic atomizing and spraying member to which the coating material leaving the edge of the inner member is attracted and ineluding an edge which is radially spaced from the edge of the inner rotatable member and from which the electrostatically atomized particles of coating material are directed on to theobject to be spray coated, an insulating member for coaxially and mechanically interconnecting said inner and said outer members, means for applying a direct high potential to said outer electrostatic member, means for feeding liquid coating material to said inner member, and an electric motor fixed to said gun for rotating at least the inner member of said head.

4. A spray gun for centrifugally and electrostatically atomizing and spraying a liquid coating material on to an object to be coated, said gun comprising a head having an inner rotatable electrically conducting member of generally cylindrical shape for effecting an initial atomization of the coating material by means of centrifugal force and including an edge by means of which the initially atomized coating material leaves said inner member, an outer generally cylindrical electrostatic atomizing and spraying member to which the coating material leaving the edge of the inner member is attracted and including an edge which is radially spaced from the edge of the inner rotatable member and from which the electrostatically atomized particles of coating material are directed on to the object to be spray coated, an insulating member for coaxially and mechanically interconnecting said inner and said outer members, means for applying a direct high potential to said outer electrostatic member, means for feeding liquid coating material to said inner member, and an electric motor fixed to said gun for rotating said head and wherein said edge of the outer electrostatic atomizing and spraying member is situated in front of the plane of the edge of the inner rotatable member and also in front of the plane containing said insulating member.

5. A gun as claimed in claim 1 wherein the outer mernher is connected to the source of high potential by means of a metallic electrode supported from the insulating body of the gun and sufficiently near to the rear surface of the said outer member to permit sparks to jump between it and said outer member.

6. A gun as claimed in claim 1, wherein the outer member is made of an electrically conducting material.

7. A gun as claimed in claim 1, wherein the outer member is made of an electrically high resistivity material.

References Cited in the file of this patent UNITED STATES PATENTS 2,658,009 Ransburg Nov. 3, 1953 2,781,279 Miller Feb. 12, 1957 2,809,902 Ransburg Oct. 15, 1957 2,922,584 Slatkin Jan. 26, 1960 2,926,106 Gauthier Feb. 23, 1960 

1. A SPRAY GUN FOR CENTRIFUGALLY AND ELECTROSTATICALLY ATOMIZING AND SPRAYING A LIQUID COATING MATERIAL ON TO AN OBJECT TO BE COATED, SAID GUN COMPRISING A HEAD HAVING AN INNER ROTATABLE ELECTRICALLY CONDUCTING MEMBER FOR EFFECTING AN INITIAL ATOMIZATION OF THE COATING MATERIAL BY MEANS OF CENTRIFUGAL FORCE AND INCLUDING AN EDGE BY MEANS OF WHICH THE INITIALLY ATOMIZED COATING MATERIAL LEAVES SAID INNER MEMBER, AN OUTER ELECTROSTATIC ATOMIZING AND SPRAYING MEMBER TO WHICH THE COATING MATERIAL LEAVING THE EDGE OF THE INNER MEMBER IS ATTRACTED AND INCLUDING AN EDGE WHICH IS RADIALLY SPACED FROM THE EDGE OF THE INNER ROTATABLE MEMBER AND FROM WHICH THE ELECTROSTATICALLY ATOMIZED PARTICLES OF COATING MATERIAL ARE DIRECTED ON TO THE OBJECT TO BE SPRAY-COATED, AN INSULATING MEMBER FOR COAXIALLY AND MECHANICALLY INTERCONNECTING SAID INNER AND SAID OUTER MEMBERS, MEANS FOR APPLYING A DIRECT HIGH POTENTIAL TO SAID OUTER ELECTROSTATIC MEMBER, MEANS FOR FEEDING LIQUID COVERING MATERIAL TO SAID INNER MEMBER, AND AN ELECTRIC MOTOR FIXED TO SAID GUN FOR ROTATING AT LEAST THE INNER MEMBER OF SAID HEAD. 